Process for producing a crystalline aluminosilicate

ABSTRACT

The present invention disclosed a crystalline aluminosilicate which has the following characteristics: 
     (A) an SiO 2  /Al 2  O 3  molar ratio as determined by chemical analysis of from 5 to 11; 
     (B) a unit cell dimension of from 24.45 to 24.55 
     (C) a molar ratio of the Al contained in the zeolite framework to the total A1 contained in the aluminosilicate of from 0.3 to 0.9 calculated by the equations specified in the specification; 
     (D) an alkali metal content, in terms of oxide, of from 0.02 to 1.5% by weight; 
     (E) an X-ray diffraction pattern having peaks characteristic of zeolite Y; and 
     (F) an ignition loss of from 0.5 to 20% by weight; and 
     a process for producing the same, and a catalyst employing the same for the catalytic cracking of a hydrocarbon oil and the said catalyst which contains at least one metal selected from rare earth metals and alkaline earth metals.

This is a continuation of application Ser. No. 08/471,201 filed Jun. 6,1995, now U.S. Pat. No. 5,646,082 which is a continuation of applicationSer. No. 08/080,308, filed Jun. 24, 1993 now abandoned.

FIELD OF THE INVENTION

The present invention relates to a crystalline aluminosilicate, aprocess for producing the same, and a catalyst for the catalyticcracking of a hydrocarbon oil which catalyst employs thealuminosilicate. More particularly, this invention relates to acrystalline aluminosilicate having excellent hydrothermal stability, aprocess for producing the aluminosilicate by applying a thermal load tostabilized zeolite Y under specific conditions, and a catalytic crackingcatalyst employing the aluminosilicate which catalyst provides excellentcatalytic conversion of a bottom fraction (heavy distillate oil), isexcellent in selectivity for hydrogen and coke (i.e., capable ofeffectively controlling the generation of hydrogen and coke (forming alower amount of hydrogen and coke)), and can yield gasoline having a lowolefin content.

BACKGROUND OF THE INVENTION

In the petroleum refining industry, the role of the catalytic crackingprocess generally is to crack a hydrocarbon oil by bringing it intocontact with a catalyst to thereby produce cracked gasoline in highyield.

As the feedstock oil, vacuum gas oil (VGO) has mostly been usedconventionally.

Recently however, the crude oil situation and the trend of the petroleumproduct market have led to a growing desire for a process in whichbottoms (heavy distillate) obtained in an atmospheric or vacuumdistillation (hereinafter referred to as bottoms) are also used as thefeedstock oil to be cracked and light cracked oil fractions (hereinafterreferred to as LCO) are increased simultaneously with the gasolinefraction.

Catalysts designed for attaining improved conversion of bottoms havebeen proposed which include a catalyst comprising a mixture ofsilica-alumina, γ-alumina, boehmite, or the like as an inorganic oxidematrix which is one of the catalyst components and stabilized zeolite Y,and a catalyst comprising a mixture of an alumina-magnesia matrix and acrystalline aluminosilicate (see JP-A-58-163439 and JP-A-1-111446). (Theterm "JP-A" as used herein means an "unexamined published Japanesepatent application".)

On the other hand, the present inventors proposed a crystallinealuminosilicate which has a specific structure obtained by applying acertain thermal load to a specific stabilized zeolite Y (JP-A-4-59616).

DESCRIPTION OF THE PRIOR ART

However, the catalytic cracking of a bottom using a catalyst containinga matrix of silica-alumina or the like for attaining improved conversionhas a problem of providing an increased amount of hydrogen and coke andthis not only reduces the yields of the desired liquid products such asgasoline and LCO, but also results in difficulties in operating theunit.

The above process is also disadvantageous gasoline quality because thegasoline has an increased olefin content, which necessarily lowers thequality.

On the other hand, when a catalyst containing the crystallinealuminosilicate having a specific structure is used, whichaluminosilicate was proposed by the present inventors, a bottom can becracked while controlling the generation of hydrogen and coke and anolefin content lower than conventional ones can be attained. Thus,quality deterioration can be avoided.

However, the technique described in JP-A-4-59616 necessitates a hightemperature treatment which should be conducted under severe conditions.Under these circumstances, there is a desire for a catalytic crackingcatalyst which can be produced by a simpler method and which hasperformances equal to or higher than those of conventional crackingcatalysts, that is, which provides high catalytic conversion and iscapable of attaining a reduction in olefin content.

The present invention has been completed in order to satisfy suchdesire. Accordingly, an object of the present invention is to provide acrystalline aluminosilicate which has excellent hydrothermal stabilityand which, when used as a component of a catalyst for the catalyticcracking of a hydrocarbon oil, especially a bottom, brings about highcatalytic conversion and can heighten the yields of gasoline and LCOwhile attaining a low olefin content in the gasoline and controlling thegeneration of hydrogen and coke. Other objects of the present inventionare to provide a process for producing the aluminosilicate fromstabilized zeolite Y and to provide the catalyst employing thealuminosilicate and having the properties described above.

SUMMARY OF THE INVENTION

As a result of intensive studies made to attain the aforementionedobjects, the present inventors found that a crystalline aluminosilicateobtained from stabilized zeolite Y having specific properties byapplying thereto a thermal load under specific conditions milder thanthose of JP-A-4-59616 has characteristic properties with respect to themolar ratio of the Al contained in the zeolite framework to the totalAl, ignition weight loss, and unit cell dimension. It was also foundthat when a mixture of the crystalline aluminosilicate having suchcharacteristic properties with an inorganic oxide matrix is used as acatalyst for the catalytic cracking of a hydrocarbon oil, especially abottom, it shows an activity equal to or higher than that attained bythe aforementioned prior art technique in which a high temperature loadis applied, so that the mixture not only attains a reduced olefincontent but also enables the oil to be efficiently cracked to yieldgasoline and LCO in higher yields while effectively controlling thegeneration of hydrogen and coke. The present invention has beencompleted based on these findings.

The present invention provides, in the first aspect thereof, acrystalline aluminosilicate having the following characteristics:

(A) the SiO₂ /Al₂ O₃ molar ratio as determined by chemical analysis isfrom 5 to 11;

(B) the unit cell dimension is from 24.45 to 24.55 Å;

(C) the molar ratio of the Al contained in the zeolite framework to thetotal Al contained in the aluminosilicate is from 0.3 to 0.9, said molarratio being calculated using equations (1) to (3) given below;

(D) the alkali metal content, in terms of oxide, is from 0.02 to 1.5% byweight;

(E) the X-ray diffraction pattern has characteristic peaks of zeolite Y;and

(F) the ignition loss is from 0.5 to 20% by weight; and

also provides a catalyst for the catalytic cracking of a hydrocarbon oilwhich catalyst employs the crystalline aluminosilicate.

    N.sub.Al =(a.sub.0 -2.425)/0.000868                        (1)

a₀ : the unit cell dimension (nm)

N_(Al) : the number of Al atoms per unit cell

    (Si/Al )=(192-N.sub.Al)/N.sub.Al                           ( 2)

192: the number of Si and Al atoms per unit cell of zeotite Y

(Al in the zeolite framework)/(total Al )= (Si/Al ) determined bychemical analysis!/ (Si/Al ) determined using equation (2)!(3)

Equation (1) above is a quotation from H. K. Beyer et al., J. Chem.Soc., Faraday Trans., Jan., 1, 1985, (81), p. 2899.

In the second aspect of the present invention, the present inventionprovides a catalyst for use in the catalytic cracking of a hydrocarbonoil comprising (i) the crystalline aluminosilicate described above or(ii) the crystalline aluminosilicate described above and an inorganicoxide matrix and, incorporated in the catalyst, at least one metalselected from rare earth metals and alkaline earth metals.

In the third aspect of the present invention, a process for producingthe crystalline aluminosilicate according to the first aspect of theinvention is provided which comprises calcining stabilized zeolite Y ina temperature range of from 400° to 590° C. for 5 to 300 minutes whilecontrolling the decrease in the crystallinity of said stabilized zeoliteY to 20% or less, said stabilized zeolite Y initially having an SiO₂/Al₂ O₃ molar ratio of from 5 to 11, a unit cell dimension of from 24.50to 24.72 Å, and an alkali metal content in terms of oxide of from 0.02to 1.5% by weight.

BRIEF EXPLANATION OF THE DRAWING

The sole FIGURE is an X-ray diffraction pattern of the crystallinealuminosilicate (HZ-1) obtained by applying a thermal shock thereto,taken with a Cu K.sub.α radiation.

DETAILED DESCRIPTION OF THE INVENTION

The starting material for the crystalline aluminosilicate according tothe present invention is stabilized zeolite Y which shows improvedstability in crystallinity and which can be obtained by hydrothermallytreating zeolite Y several times and, if required, further treating theresulting zeolite Y with at least one of a mineral acid such ashydrochloric acid, a base such as sodium hydroxide, a salt such aspotassium fluoride, and a chelating agent such asethylenediaminetetraacetic acid (EDTA).

The stabilized zeolite Y may, of course, be one obtained by treatingzeolite Y with a silicon compound such as ammonium hexafluorosilicate(NH₄)₂ SiF₆ ! or silicon tetrachloride (SiCl₄) or one obtained bytreating zeolite Y with a silicon-free compound such as EDTA or phosgene(COCl₂).

The stabilized zeolite Y for use as the slatting material has an SiO₂/Al₂ O₃ molar ratio of from about 5 to 11, preferably from 5.6 to 9, aunit cell dimension of about from 24.50 to 24.72 Å, preferably from24.55 to 24.68 Å, and an alkali metal content in terms of oxide of aboutfrom 0.02 to 1.5% by weight, preferably about from 0.05 to 1.0% byweight.

The crystal structure of this stabilized zeolite Y is basically the sameas that of natural faujasite-type zeolite. Stabilized zeolite Y isgenerally represented by the following formula in terms of oxide molarproportion:

    (0.02-1.0)R.sub.2 /m O·Al.sub.2 O.sub.3 ·(5-11) SiO.sub.2 ·(5-8)H.sub.2 O

R: an ion selected from Na, K, and other alkali metal ions

m: the valence of R

Thus, the stabilized zeolite Y for use as a starting material in thepresent invention corresponds to those having a low R_(2/m) O content,i.e., having an R_(2/m) O proportion of from 0.0015 to 0.25 as shown inthe formula.

That is, the stabilized zeolite Y for use in the present invention hasthe characteristics summarized in Table 1.

                  TABLE 1                                                         ______________________________________                                                                     Preferred                                        Characteristics  Range       Range                                            ______________________________________                                        Bulk SiO.sub.2 /Al.sub.2 O.sub.3 molar                                                         about 5 to 11                                                                             about 5.6 to 9                                   ratio as determined by                                                        chemical analysis                                                             Unit cell dimension (Å)                                                                    about 24.50 about 24.55                                                       to 24.72    to 24.68                                         Alkali metal content (wt %)                                                                    about 0.02  about 0.05                                       (in terms of oxide)                                                                            to 1.5      to 1.0                                           ______________________________________                                    

The crystalline aluminosilicate of the present invention which has thecharacteristics specified hereinabove can be obtained by applying aspecific thermal load (hereinafter occasionally referred to as "heatshock") to the stabilized zeolite Y described above.

The thermal load may be applied by calcining the stabilized zeolite Y ina temperature range of about from 400° to 590° C., preferably about from450° 570° C., for a duration of about from 5 to 300 minutes, preferablyabout from 5 to 100 minutes, provided that the decrease in crystallinityis controlled at about 20% or less, preferably at about 15% or less.

If too low a temperature is used, the calcination fails to yield acrystalline aluminosilicate having the characteristics specifiedhereinabove. On the other hand, if the calcination is conducted at toohigh a temperature or for too long a duration, the crystal structure ofthe zeolite is destroyed and hence a crystalline aluminosilicate havingthe above-specified characteristics cannot be obtained.

In general, the heat shock is applied in either an electric furnace or akiln under an air or nitrogen or vapor atmosphere.

A proper amount of moisture accelerates de-alumination and hence a heatshock can be applied at relatively low temperatures within the rangespecified above.

It is desirable to conduct the heat shock application under suchconditions that the crystal structure of the zeolite is notsubstantially destroyed. Specifically, the treatment is conducted undersuch conditions that the crystallinity of the stabilized zeolite Ydecreases by about 20% or less, preferably about 15% or less.

The crystallinity of the stabilized zeolite Y is determined inaccordance with ASTM D-3906 (Standard Test Method for Relative ZeoliteDiffraction Intensities).

Illustratively stated, zeolite Y (having an Si/Al ratio of 5.0, a unitcell dimension of 24.58 Å, and an Na₂ O content of 0.3% by weight) isused as the standard material, and the crystallinity of the testmaterial is expressed as the ratio of the test material's X-raydiffraction intensity to the standard material's X-ray diffractionintensity.

The decrease in crystallinity for the thermally shocked stabilizedzeolite Y according to the present invention can then be calculatedunsing the following equation.

    Decrease in crystallinity (%)= ##EQU1## A: Crystallinity of the stabilized zeolite Y B: Crystallinity of the thermally shocked crystalline aluminosilicate

In the above equation, the thermally shocked crystalline aluminosilicatemeans the crystalline aluminosilicate obtained by applying a heat shockto stabilized zeolite Y; this applies hereinafter.

In applying a heat shock, the heating rate is not particularly limited.For example, the stabilized zeolite Y as the raw material may be placedin a furnace which has been heated to a temperature in theabove-specified range. Alternatively, the stabilized zeolite Y may beplaced in a furnace at room temperature and then gradually heated to thepredetermined temperature.

The thermally shocked crystalline aluminosilicate may be mixed with aninorganic oxide matrix, as will be described later, before beingsubjected to the catalytic cracking of a hydrocarbon oil. Al though thetime when a heat shock is applied is not particularly limited, itpreferably is prior to the mixing with the matrix for furthereffectiveness.

The application of a heat shock in the present invention should bedistinguished from the heat treatment of catalysts which is performedunder severe conditions in order to establish the simulated equilibriumstate prior to the performance evaluation of the catalysts.

As described above, the thermally shocked crystalline aluminosilicate ofthe present invention is obtained by thermally treating stabilizedzeolite Y. However, when zeolite Y is used so as to directly yield thecrystalline aluminosilicate of this invention through heat treatment,the desired aluminosilicate cannot be obtained because the crystalstructure is destroyed.

Although the reason why zeolite Y cannot be directly converted into thedesired aluminosilicate has not been fully elucidated, it is presumedthat in order to obtain the thermally shocked crystallinealumino-silicate of the present invention, the crystal structure ofstabilized zeolite Y must be established first. That is, zeolite Y isheated to first convert its crystal structure to that of stabilizedzeolite Y and, after the resulting crystal structure has become stable,the stabilized zeolite Y is then thermally treated.

The thermally shocked crystalline aluminosilicate of the presentinvention, which can be obtained by the method described above, is anovel crystalline aluminosilicate having the following characteristics.

That is, the crystalline aluminosilicate has a bulk SiO₂ /Al₂ O₃ molarratio, as determined by chemical analysis, of about from 5 to 11,preferably about from 5.6 to 9.

The unit cell dimension of the crystalline aluminosilicate is about from24.45 to 24.55 Å, preferably about from 24.45 to 24.53 Å. This unit celldimension can be determined from X-ray diffraction peaks in accordancewith ASTM D-3942/85. Too large values of this dimension result in poorhydrothermal resistance.

In the crystalline aluminosilicate, the molar ratio of the Al containedin the zeolite framework to the total Al contained in thealuminosilicate is about from 0.3 to 0.9, preferably about from 0.4 to0.8. The value of this molar ratio can be calculated from the SiO₂ /Al₂O₃ molar ratio as determined by chemical analysis and from the unit celldimension, using equations (1) to (3) given hereinabove (see theaforementioned H. K. Bayer et al., J. Chem. Soc., Faraday Trans., Jan.,1, 1985, (81), 2899).

It should be noted that the molar ratio of the Al contained in thezeolite framework to the total Al can also be calculated using otherequations, but the value thus determined differs from that obtained withequations (1) to (3).

Provided that the bulk SiO₂ /Al₂ O₃ molar ratio is the same, too low aratio of the Al content in the zeolite framework to the total Al resultsin a crystalline aluminosilicate having poor catalytic activity.Furthermore, since this situation signifies an increase in nonframeworkAl content, i.e., an increase in amorphous Al content, it results in thecatalytic selectivity similar to that of an amorphous catalyst. Such acatalyst increases hydrogen and coke made.

On the other hand, if the molar ratio of the Al contained in the zeoliteframework to the total Al is too high, this poses a problem that thecrystalline aluminosilicate shows poor catalytic conversion of bottomsalthough it can yield gasoline having a low olefin content.

The thermally shocked crystalline aluminosilicate has an alkali metalcontent, in terms of oxide, of about from 0.02 to 1.5% by weight,preferably about from 0.05 to 1.0% by weight.

Alkali metal contents below about 0.02% by weight in terms of oxide areundesirable because the crystal structure becomes apt to be damaged.

If too large an amount of alkali metal is present in the thermallyshocked crystalline aluminosilicate, not only is the catalytic activitylowered, but also heavy metals such as nickel and vanadium, which arecommonly present in the feedstock oil, particularly in heavy oil, areapt to deposit on the catalyst to decrease the activity.

The crystalline aluminosilicate of the present invention has an ignitionloss of about from 0.5 to 20% by weight, preferably about from 1 to 10%by weight. p This ignition loss is determined using the followingequation.

    Ignition loss (wt%)=L/W×100

L: Weight loss of the sample caused by placing it in 1,000° C. airatmosphere in electric furnace for 1 hour

W: Initial weight of the sample (after dried at 110° C. for 24 hours,allowed to stand at room temperature in air for 1 week)

If the value of ignition loss is too high, the thermally shockedcrystalline aluminosilicate is apt to hold a larger amount of water andhence has poor hydrothermal stability. Consequently, the hydrocarbon oilcracking catalyst of the present invention comes to have a reduced life.

The characteristic features of the thermally shocked crystallinealuminosilicate of the present invention, which has been obtained byapplying a specific thermal load to stabilized zeolite Y as describedabove, reside in that it has a unit cell dimension of about from 24.45to 24.55 Å, which is clearly smaller than the unit cell dimension ofabout from 24.50 to 24.72 Å for stabilized zeolite Y, and that it has amolar ratio of the Al contained in the zeolite framework to the total Alof about from 0.3 to 0.9 and also has an ignition loss of about from 0.5to 20% by weight.

The characteristics of the thermally shocked crystalline aluminosilicateof the present invention are summarized in Table 2.

                  TABLE 2                                                         ______________________________________                                                                     Preferred                                        Characteristics  Range       Range                                            ______________________________________                                        Bulk SiO.sub.2 /Al.sub.2 O.sub.3 molar                                                         about 5 to 11                                                                             about 5.6 to 9                                   ratio as determined by                                                        chemical analysis                                                             Al in zeolite framework/                                                                       about 0.3   about 0.4                                        total Al atomic ratio                                                                          to 0.9      to 0.8                                           Unit cell dimension (Å)                                                                    about 24.45 about 24.45                                                       to 24.55    to 24.53                                         Alkali metal content (wt %)                                                                    about 0.02  about 0.05                                       (in terms of oxide)                                                                            to 1.5      to 1.0                                           Ignition loss (wt %)                                                                           about 0.5   about 1                                                           to 20       to 10                                            ______________________________________                                    

The thermally shocked crystalline aluminosilicate of the presentinvention gives an X-ray diffraction pattern as shown in FIG. 1.

In FIG. 1, numerals 1, 2, and 3 denote the three principal peaks atlattice spacings (d) of 14.1±0.2 Å, 5.61±0.1 Å, and 3.72±0.1 Å.

The peaks in the X-ray diffraction pattern of FIG. 1 are read as shownin Table 3.

                  TABLE 3                                                         ______________________________________                                        Lattice spacing, d (Å)                                                                   Relative intensity (I/I.sub.0)*                                ______________________________________                                        14.1 ± 0.2  s-vs                                                           8.6 ± 0.2   m-s                                                            7.4 ± 0.1   m-s                                                            5.61 ± 0.1  s-vs                                                           4.70 ± 0.1  m-s                                                            4.32 ± 0.1  m-s                                                            3.86 ± 0.1  w-m                                                            3.72 ± 0.1  s-vs                                                           3.42 ± 0.1  w-m                                                            3.26 ± 0.1  m-s                                                            2.98 ± 0.1  w-m                                                            2.87 ± 0.1  w-m                                                            2.82 ± 0.1  m-s                                                            2.72 ± 0.1  w-m                                                            2.68 ± 0.1  w                                                              2.60 ± 0.1  w-m                                                            2.56 ± 0.1  w                                                              2.35 ± 0.1  w                                                              ______________________________________                                         *vs: very strong; s: strong; m: medium; w: weak                          

The hydrocarbon oil cracking catalyst according to the present inventioncomprises a mixture of the thermally shocked crystalline aluminosilicatedescribed above and an inorganic oxide matrix.

Examples of the inorganic oxide matrix include silica, alumina, boria,chromia, magnesia, zirconia, titania, silica-alumina, silica-magnesia,silica-zirconia, chromia-alumina, titania-alumina, titania-silica,titania-zirconia, alumina-zirconia, and mixtures thereof. The inorganicoxide matrix may further contain at least one clay selected frommontmorillonite, kaolin, halloysite, bentonite, attapulgite, bauxite,and the like.

The mixture (i.e., the catalyst of the present invention) can beproduced by any conventional method. In a representative method, thethermally shocked crystalline aluminosilicate is added into an aqueousslurry of an adequate inorganic oxide matrix, e.g., a silica-aluminahydrogel, silica sol, or alumina sol, and the resulting mixture ishomogenized by stirring and then spray-dried to obtain a micro particlecatalyst.

In such catalyst production, the ingredients may be mixed in such aproportion that the catalyst to be obtained will have a thermallyshocked crystalline aluminosilicate content of about from 5 to 60% byweight, preferably about from 10 to 50% by weight, and an inorganicoxide matrix content of about from 40 to 95% by weight, preferably aboutfrom 50 to 90% by weight.

If the thermally shocked crystalline aluminosilicate content is belowabout 5% by weight, the effect expected of hydrocarbon oil crackingcatalysts cannot be obtained. If the content thereof is higher thanabout 60% by weight, the proportion of the inorganic oxide matrix is sosmall that the catalyst has poor strength to cause problems concerning,e.g., unit operation, such as flying off of the catalyst and inclusionof the catalyst into the product.

According to one aspect of the present invention, the catalyst describedabove is also characterized as containing at least one metal selectedfrom the group consisting of rare earth metals and alkaline earthmetals.

Examples of the rare earth metals include scandium, yttrium, lanthanum,cerium, oraseodymium, neodymium, samarium, and gadolinium. These may beused alone or as a mixture of two or more thereof.

Examples of the alkaline earth metals include beryllium, magnesium,calcium, strontium, barium, and radium. These may be used either aloneor as a mixture of two or more thereof. Preferred of these aremagnesium, calcium, and a mixture thereof.

It is possible to use a mixture of at least one of such rare earthelements with at least one of such alkaline earth metals. However, it ispreferred to use the rare earth metals.

Embodiments of such catalyst containing at least one of the rare earthand alkaline earth metals include one in which the thermally shockedcrystalline aluminosilicate, as one of the catalyst components, has beenconverted to a metal modified form by partly or wholly ion-exchangingthe thermally shocked crystalline aluminosilicate with the metal(s) orby impregnating the thermally shocked crystalline aluminosilicate withthe metal(s), and also include one in which the catalyst itself has beenion-exchanged or impregnated with the metal(s).

For the ion exchange or metal impregnation of either the thermallyshocked crystalline aluminosilicate or the catalyst with at least one ofthe metals specified above, any conventional method may be used.

For example, either the ion exchange or the metal impregnation can beaccomplished by a method in which the thermally shocked crystallinealuminosilicate or the catalyst is impregnated with or immersed in anaqueous solution of at least one of such compounds of lanthanum,magnesium, calcium, etc. as chlorides, nitrates, sulfates, and acetates,with heating if necessary.

In either the ion exchange or the metal impregnation, the amount of themetal(s) to be incorporated is about from 0.01 to 10% by weight,preferably about from 0.05 to 7% by weight, in terms of oxide based onthe total amount of the catalyst, i.e., the crystallinealuminosilicate/inorganic oxide matrix mixture.

When the incorporated metal amount is expressed in terms of the degreeof metal exchange for the crystalline aluminosilicate, it is about from2 to 95%, preferably about from 5 to 80%. This metal exchange degree (%)is defined by the following equation.

    Metal exchange degree (%)=A/B×100

A: Metal content of the aluminosilicate

B: Metal content of the aluminosilicate after all ion-exchangeable siteshave been displaced by the metal

Another feature of the aluminosilicate according to the presentinvention resides in that the incorporation of one or more of rare earthand alkaline earth metals into the aluminosilicate is easier than thatinto conventional aluminosilicates treated at temperatures as high as600° to 1,200° C.

In other words, the aluminosilicate of the present invention isadvantageous in that when this aluminosilicate and the conventionalaluminosilicates are treated under the same conditions for incorporatinga specific metal thereinto, the metal can be incorporated into thealuminosilicate of the present invention in a larger amount.

The metal ion exchange or metal impregnation described above enables theproduction of gasoline with a lower olefin content. This effect,however, is not brought about if the incorporated metal amount is toosmall. On the other hand, even if the incorporated metal amount is toolarge, the effect is not substantially heightened any more.

When the aluminosilicate of the present invention is compared incatalytic activity with conventional aluminosilicates treated attemperatures as high as 600° to 1,200° C., the former aluminosilicateshows far higher activity. The same activity as the conventional one cantherefore be attained with the aluminosilicate of the invention in anamount smaller than the conventional ones.

The catalytic cracking of a hydrocarbon oil with the above-describedcatalyst of the present invention may be carried out by bringing thehydrocarbon oil (a mixture of hydrocarbons) which boils at a temperaturehigher than the boiling range for gasoline into contact with thecatalyst.

Examples of the hydrocarbon mixture which boils at a temperature higherthan the gasoline boiling range include gas oil fractions obtained bythe atmospheric or vacuum distillation of crude oil, topping residue andvacuum residue. Examples thereof further include coker gas oil, solventdeasphalted oils, solvent deasphalted residues, oils extracted from tarsand or oil shale, and product oils from coal liquefaction.

In a commercial-scale catalytic cracking process, the catalyst of thepresent invention described above is continuously circulated through acatalytic cracking unit comprising two vessels, i.e., a vertically setcracking reactor and a catalyst regenerator.

The hot regenerated catalyst discharged from the catalyst regenerator ismixed with the hydrocarbon oil to be cracked, and the mixture is thenled upward through the cracking reactor.

As a result of the cracking, a carbonaceous substance generally calledcoke deposits on the catalyst and thereby deactivates it. Thedeactivated catalyst is separated from the cracking products, subjectedto stripping, and then transported into the catalyst regenerator.

The used catalyst circulated into the catalyst regenerator isregenerated by burning off the coke on the catalyst in air. The thusregenerated catalyst is then recirculated into the cracking reactor.

On the other hand, the cracking products are separated into dry gas,LPG, a gasoline fraction, and one or more heavy distillates such aslight cycle oil (LCO), heavy cycle oil (HCO), and slurry oil.

These heavy distillates may, of course, be further reacted byrecirculating them into the cracking reactor.

It is desirable to operate the cracking reactor of the above-describedcatalytic cracking unit under conditions of a pressure of about fromatmospheric pressure to 5 Kg/cm², a temperature of about from 400° to600° C., preferably about from 450° to 550° C., and a catalyst/feedstockhydrocarbon oil weight ratio of about from 2 to 20, preferably aboutfrom 4 to 15.

As described above in detail, the catalyst of the present invention,which contains the thermally shocked crystalline aluminosilicate of theinvention obtained from stabilized zeolite Y by the process of thepresent invention in which a specific thermal load is applied to the rawmaterial, is superior to conventional catalysts in activity in thecatalytic cracking of a hydrocarbon oil, particularly a bottom, and canyield a gasoline having a low olefin content.

Furthermore, since the bottom-cracking ability of the catalyst of thepresent invention can be improved further, gasoline and light cycle oil(LCO), which corresponds to kerosene and gas oil, can be produced inhigher yields while effectively controlling the formation of hydrogenand coke.

The present invention is now described in further detail by referring tothe following Examples and Comparative Examples, but it should beunderstood that the present invention is not construed as being limitedthereto. Unless otherwise indicated, all percents and parts in thefollowing are by weight.

EXAMPLE 1 (Production of thermally shocked crystalline aluminosilicateHZ-1)

A stabilized zeolite Y having an SiO₂ /Al₂ O₃ molar ratio of 6,containing 0.58% by weight in terms of oxide of an alkali metal, andhaving a unit cell dimension of about 24.63 Å was calcined (heat shock)at 540° C. for 10 minutes in an air atmosphere in an electric furnaceunder ordinary pressure, thereby producing a thermally shockedcrystalline aluminosilicate.

The product had the X-ray diffraction pattern characteristic of zeoliteY.

The crystallinity of the stabilized zeolite y used as the raw materialwas 118% (with the crystallinity of zeolite Y as standard being taken as100%), while that of the thermally shocked product was 100% the decreasein crystallinity was 15%).

This thermally shocked crystalline aluminosilicate is designated asHZ-1, and the characteristics thereof are summarized in Table 4.

                  TABLE 4                                                         ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio                                                          6.0                                                        Al in zeolite framework/                                                                         0.46                                                       total Al molar ratio                                                          Unit cell dimension (Å)                                                                      24.47                                                      Alkali metal content (wt %)                                                                      0.58                                                       Ignition loss (wt %)                                                                             5.80                                                       ______________________________________                                    

EXAMPLE 2 (Production of thermally shocked crystalline aluminosilicateHZ-2)

A thermally shocked crystalline aluminosilicate was produced in the samemanner as in Example 1 except that the calcination temperature waschanged to 480° C.

The product had the X-ray diffraction pattern characteristic of zeoliteY.

The crystallinity of the thermally shocked product was 105% ascalculated on the same basis as in Example 1 (the decrease incrystallinity was 11%).

This thermally shocked crystalline aluminosilicate is designated asHZ-2, and the characteristics thereof are summerized in Table 5.

                  TABLE 5                                                         ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio                                                          6.0                                                        Al in zeolite framework/                                                                         0.55                                                       total Al molar ratio                                                          Unit cell dimension (Å)                                                                      24.51                                                      Alkali metal content (wt %)                                                                      0.58                                                       Ignition loss (wt %)                                                                             5.07                                                       ______________________________________                                    

COMPARATIVE EXAMPLE 1 (Production of the high temperature thermallyshocked crystalline aluminosilicate HZ-3)

A thermally shocked crystalline aluminosilicate was produced in the samemanner as in Example 1 except that the calcination temperature waschanged to 750° C.

The product had the X-ray diffraction pattern characteristics of zeoliteY.

The crystallinity of the thermally shocked product was 94% as calculatedon the same basis as in Example 1 (the decrease in crystallinity was20%).

This thermally shocked crystalline aluminosilicate is designated asHZ-3, and the characteristics thereof are summarized in Table 6.

                  TABLE 6                                                         ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio                                                          6.0                                                        Al in zeolite framework/                                                                         0.32                                                       total Al molar ratio                                                          Unit cell dimension (Å)                                                                      24.41                                                      Alkali metal content (wt %)                                                                      0.58                                                       Ignition loss (wt %)                                                                             3.38                                                       ______________________________________                                    

EXAMPLE 3 AND COMPARATIVE EXAMPLES 2 AND 3 (Evaluation of hydrothermalstability and exchanged ion amount for aluminosilicates)

(Evaluation of Hydrothermal Stability)

Aluminosilicate HZ-2 according to the present invention was evaluatedfor hydrothermal stability along with HZ-3 and the starting material,stabilized zeolite Y, for comparison. The evaluation was conducted underthe following conditions, for determining which the actual useconditions in commercial unit were taken in account. The results aresummarized in Table 7.

Conditions

Temperature: 600°, 700°, and 800° C.

Atmosphere: 100% steam

Duration : 0 hours

Evaluation item: After the treatment of the above duration, thealuminosilicate was checked for (1) a change in crystallinity, and (2) achange in unit cell dimension.

                  TABLE 7                                                         ______________________________________                                                                          Comparative                                                                   Example 3                                                           Comparative                                                                             Starting mate-                                           Example 3  Example 2 rial (Stabilized                                         HZ-2       HZ-3      Zeolite Y)                                  ______________________________________                                        SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio                                                    6.0        6.0       6.0                                         Crystallinity (%)                                                                          105        94        118                                         600° C. treatment                                                                   102        95        110                                         700° C. treatment                                                                   100        96        81                                          800° C. treatment                                                                   94         94        55                                          Unit cell dimension (Å)                                                                24.51      24.41     24.63                                       600° C. treatment                                                                   24.39      24.36     24.38                                       700° C. treatment                                                                   24.36      24.34     24.34                                       800° C. treatment                                                                   24.34      24.29     24.25                                       ______________________________________                                    

The results show that HZ-2, to which a thermal load had been appliedunder the conditions specified in the present invention, had excellenthydrothermal stability. That is, it was almost equal to HZ-3 inhydrothermal stability and provided a slighter change in bothcrystallinity and unit cell dimension than stabilized zeolite Y athigher treating temperatures.

(Evaluation of Exchanged Ion Amount)

Using lanthanum as a rare earth element, the amount of ion exchangedunder the same conditions given below was determined. The results areshown in Table 8.

Conditions

Ion exchange solution: 500 ml of 0.2N LaCl₃ ·7H₂ O solution

Treating temperature: 60° C.

Exchange duration: 15 minutes

Amount of aluminosilicate: 20 g

                  TABLE 8                                                         ______________________________________                                                    HZ-2      HZ-3                                                    Aluminosilicate                                                                           (Example 3)                                                                             (Comparative Example 2)                                 ______________________________________                                        La.sub.2 O.sub.3 (wt %)                                                                   3.07      2.27                                                    ______________________________________                                    

Table 8 shows that a larger La₂ O₃ amount is attained with thealuminosilicate of the present invention, that is, the incorporation ofthe rare earth metal into the aluminosilicate of the invention iseasier.

EXAMPLE 4 (Preparation of catalyst A)

A mixture of 2,315 g of water and 2,335 g of a 30 wt % silica sol wasprepared with stirring, and sulfuric acid was added thereto to adjustthe pH to 1.8. Thereto were then added 1,736 g (dry basis) of kaolin,1,042 g (dry basis) of the HZ-1 obtained in Example 1, and 3,000 g ofwater. The resulting mixture was homogenized by stirring.

The mixture thus obtained was spray-dried to yield a micro particle,which was then washed with 25 liters of distilled water.

The resulting powder was dried in air at 115° C. for 16 hours, therebyobtaining a catalyst according to the present invention (hereinafterreferred to as catalyst A).

EXAMPLE 5 (Preparation of catalyst B)

The same procedures as in Example 4 were conducted except that the HZ-2obtained in Example 2 was used in place of HZ-1. Thus, a catalystaccording to the present invention (hereinafter referred to as catalystB) was obtained.

COMPARATIVE EXAMPLE 4 (Preparation of catalyst C)

The same procedures as in Example 4 were conducted except that the HZ-3obtained in Comparative Example 1 was used in place of HZ-1. Thus, acomparative catalyst (hereinafter referred to as catalyst C) wasobtained.

COMPARATIVE EXAMPLE 5 (Preparation of catalyst D)

The same procedures as in Example 4 were conducted except that thestabilized zeolite Y employed as a starting material in Example 1 wasused in place of HZ-1. Thus, a comparative catalyst (hereinafterreferred to as catalyst D) was obtained.

EXAMPLE 6 (Preparation of catalyst E)

A mixture of 2,315 g of water and 2,335 g of a 30 wt % silica sol wasprepared with stirring, and sulfuric acid was added thereto to adjustthe pH to 1.8. Thereto were then added 1,910 g (dry basis) of kaolin,868 g (dry basis) of the HZ-1 obtained in Example 1, and 3,000 g ofwater. The resulting mixture was homogenized by stirring.

The mixture thus obtained was spray-dried to yield a fine powder as acatalyst precursor.

The whole precursor was subjected to ion exchange using 30 liters of anaqueous solution of a rare earth metal chloride which solution had acontent of the chloride of 10 g per 100 ml. The rare earth metalchloride had the composition shown in Table 9; the same rare earth metalchloride was used in the following Examples and Comparative Examples.The ion exchange was conducted at about 90° C. for 30 minutes.

The powder was thereafter recovered by filtration, washed with water,and then dried in air at 115° C. for 16 hours, thereby obtaining acatalyst according to the present invention (hereinafter referred to ascatalyst E).

                  TABLE 9                                                         ______________________________________                                        Composition of the rare earth metal chloride                                  (wt %, in terms of oxide)                                                     CeO.sub.2                                                                             La.sub.2 O.sub.3                                                                            Nd.sub.2 O.sub.3                                                                      Pr.sub.8 O.sub.11                               ______________________________________                                        52.9    22.9          18.8    5.5                                             ______________________________________                                    

EXAMPLE 7 (Preparation of catalyst F)

A mixture of 2,315 g of water and 2,335 g of a 30 wt % silica sol wasprepared with stirring, and sulfuric acid was added thereto to adjustthe pH to 1.8. Thereto were then added 2,084 g (dry basis) of kaolin,695 g (dry basis) of the HZ-2 obtained in Example 2, and 3,000 g ofwater. The resulting mixture was homogenized by stirring.

The mixture thus obtained was spray-dried to yield a fine powder as acatalyst precursor.

The whole precursor was subjected to ion exchange using 30 liters of anaqueous solution of the rare earth metal chloride which solution had acontent of the chloride of 10 g per 100 ml. The ion exchange wasconducted at about 90° C. for 30 minutes.

The powder was thereafter recovered by filtration, washed with water,and then dried in air at 115° C. for 16 hours, thereby obtaining acatalyst according to the present invention (hereinafter referred ascatalyst F).

COMPARATIVE EXAMPLE 6 (Preparation of catalyst G)

A mixture of 2,315 g of water and 2,335 g of a 30 wt% silica sol wasprepared with stirring, and sulfuric acid was added thereto to adjustthe pH to 1.8. Thereto were then added 1,669 g (dry basis) of kaolin,1,111 g (dry basis) of the HZ-3 obtained in Comparative Example 1, and3,000 g of water. The resulting mixture was homogenized by stirring.

The mixture thus obtained was spray-dried to yield a fine powder as acatalyst precursor.

The whole precursor was subjected to ion exchange using 30 liters of anaqueous solution of the rare earth metal chloride which solution had acontent of the chloride of 10 g per 100 ml. The ion exchange wasconducted at about 70° C. for 30 minutes.

The powder was thereafter recovered by filtration, washed with water,and then dried in air at 115° C. for 16 hours, thereby obtaining acomparative catalyst (hereinafter referred to as catalyst G).

COMPARATIVE EXAMPLE 7 (Preparation of catalyst H)

The same procedures as in Example 6 were conducted except that the HZ-3obtained in Comparative Example 1 was used in place of HZ-1. Thus, acomparative catalyst (hereinafter referred to as catalyst H) wasobtained.

COMPARATIVE EXAMPLE 8 (Preparation of catalyst I)

A mixture of 2,315 g of water and 2,335 g of a 30 wt% silica sol wasprepared with stirring, and sulfuric acid was added thereto to adjustthe pH to 1.8. Thereto were then added 1,805 g (dry basis) of kaolin,975 g (dry basis) of the stabilized zeolite Y employed as a startingmaterial in Example 1, and 3,000 g of water. The resulting mixture washomogenized by stirring.

The mixture thus obtained was spray-dried to yield a fine powder as acatalyst precursor.

The whole precursor was subjected to ion exchange using 30 liters of anaqueous solution of the rare earth metal chloride which solution had acontent of the chloride of 10 g per 100 ml. The ion exchange wasconducted at about 50° C. for 30 minutes.

The powder was thereafter recovered by filtration, washed with water,and then dried in air at 115° C. for 16 hours, thereby obtaining acomparative catalyst (hereinafter referred to as catalyst I).

EXAMPLE 8 (Preparation of catalyst J)

The same procedures as in Comparative Example 6 were conducted exceptthat the HZ-1 obtained in Example 1 was used in place of HZ-3, therebyto obtain a catalyst precursor.

The whole precursor was subjected to ion exchange using 30 liters of anaqueous solution of the rare earth metal chloride which solution had acontent of the chloride of 10 g per 100 ml. The ion exchange wasconducted at about 50° C. for 30 minutes.

The powder was thereafter recovered by filtration, washed with water,and then dried in air at 115° C. for 16 hours, thereby obtaining acatalyst according to the present invention (hereinafter referred to ascatalyst J).

COMPARATIVE EXAMPLE 9 (Preparation of catalyst K)

The same procedures as in Comparative Example 6 were conducted exceptthat the ion exchange was conducted at about 60° C. for 30 minutes.Thus, a comparative catalyst (hereinafter referred to as catalyst K) wasobtained.

Activity Test in Pilot Plant Unit

Catalysts A to K obtained above were evaluated with respect to thecatalytic cracking properties on a hydrocarbon oil using a pilot plantunit. This unit was a scaled down version of a catalytic cracking plantactually used in commercial production, which was a circulation typefluidized bed reactor comprising a cracking reactor and a catalystregenerator.

The catalysts tested were treated prior to the testing in a 100% streamatmosphere at 785° C. for 6 hours so that they reached aquasi-equilibrium state.

The feedstock oils used were a desulfurized vacuum gas oil for Examples4, 5, 6, and 7 (catalysts A, B, E, and F) and Comparative Examples 4, 5,6, 7, and 8 (catalysts C, D, G, H, and I) and a mixed oil composed of 70wt % desulfurized vacuum gas oil and 30 wt % resid desulfurizationproduct for Example 8 (catalyst J) and Comparative Example 9 (catalystK). The test was conducted using catalysts A to K using the feedstockoil, at a reaction temperature of 500° C., while circulating thecatalyst at a rate of 60 g/min. The catalyst/oil ratio (by weight) wasvaried 4 levels, i.e., 4, 7, 9.5, and 12.5, and from the results thusobtained, the results which yields 65% conversion were selected as thestandard value for comparison.

For comparing the activities, the conversion values obtained at acatalyst/oil ratio of 7 were used.

The composition of each catalyst and the results obtained are summarizedin Table 10, in which the catalysts have been divided into three groupsfor evaluation.

Group I!

(Examples 4 and 5 and Comparative Examples 4 and 5)

This group comprises catalysts A and B according to the presentinvention, catalyst C containing an aluminosilicate thermally shocked at750° C., and catalyst D containing stabilized zeolite Y used as startingmaterial.

As Table 10 clearly shows, catalysts A and B each gave almost the sameresults as those obtained with catalyst C. That is, catalysts A and Battained (i) a high activity and (ii) low olefin content.

The above results indicate that the present invention has advantagesthat as compared with the conventional techniques, stabilized zeolite Yas a starting material can be treated at a lower temperature andcatalyst production is easier because of, e.g., the less severeconditions for catalyst production.

Group II!

(Examples 6 and 7 and Comparative Examples 6 to 8)

This group comprises catalysts containing rare earth metals.

These catalysts are catalysts E and F according to the presentinvention, catalysts G and H containing an aluminosilicate thermallyshocked at 750° C., and catalyst I containing stabilized zeolite Y usedas starting material.

A comparison of catalysts E and F with catalyst G shows that catalysts Eand F needed lower aluminosilicate content to obtain the same activityand that they attained lower olefin contents. This means that thecatalysts according to the present invention have a higher activity.

A comparison of catalysts E and F with catalyst H shows that catalysts Eand F had a higher activity and attained lower olefin contents despitethe fact that the aluminosilicate contents thereof were equal to orlower than that of catalyst H. Further, as compared also with catalystI, catalysts E and F according to the present invention attained ahigher activity and lower olefin contents. Moreover, it shows thatcatalysts E and F attained lower hydrogen and coke contents and wereexcellent in the bottom cracking ability.

The above results indicate that the present invention is effective inattaining a lower olefin content in gasoline and a higher catalyticactivity than those attainable by the conventional techniques.

Group III!

(Example 8 and Comparative Example 9)

This group comprises catalysts containing the same amount of thealuminosilicate and the rare earth metal used with a heavier feedstockoil.

Although the two catalysts were almost equal in product yield and olefincontent, the catalyst according to the present invention was superior inactivity.

                                      TABLE 10                                    __________________________________________________________________________                               Comparative                                                                         Comparative                                                   Example 4                                                                          Example 5                                                                          Example 4                                                                           Example 5                                                                           Example 6                                                                          Example 7                         Catalyst         A    B    C     D     E    F                                 __________________________________________________________________________    Aluminosilicate content (wt %)                                                                 30   30   30    30    25   20                                Kaolin content (wt %)                                                                          50   50   50    50    55   60                                Silica binder content (wt %)                                                                   20   20   20    20    20   20                                Rare earth metal exchange degree (%)                                                           --   --   --    --    53   53                                Rare earth metal oxide amount (wt %)                                                           --   --   --    --    1.64 1.67                              Results of cracking                                                           Conversion (wt %)                                                                              65.2 64.5 65.2  64.7  65.2 65.4                              Hydrogen (wt %)  0.16 0.17 0.17  0.18  0.13 0.12                              C.sub.1 -C.sub.2 (wt %)                                                                        1.5  1.5  1.4   1.4   1.3  1.3                               LPG (wt %)       12.5 12.0 12.5  12.2  10.8 10.8                              Gasoline (wt %)  48.6 48.4 48.6  48.4  50.7 50.9                              LCO*.sup.1 (wt %)                                                                              23.8 23.9 24.0  23.5  24.0 23.7                              HCO+*.sup.2 (wt %)                                                                             11.0 11.6 10.9  11.8  10.8 10.9                              Coke (wt %)      2.5  2.5  2.5   2.6   2.3  2.3                               Olefins (vol %)  48.1 47.2 47.5  50.5  39.0 38.4                              Catalytic Activity*.sup.3                                                                      65   65   65    62    65   65                                Group for evaluation                                                                            I!   I!   I!    I!    II!  II!                              __________________________________________________________________________                     Comparative                                                                         Comparative                                                                          Comparative  Comparative                                         Example 6                                                                           Example 7                                                                            Example 8                                                                           Example 8                                                                            Example 9                          Catalyst         G     H      I     J      K                                  __________________________________________________________________________    Aluminosilicate content (wt %)                                                                 32    25     28    32     32                                 Kaolin content (wt %)                                                                          48    55     52    48     48                                 Silica binder content (wt %)                                                                   20    20     20    20     20                                 Rare earth metal exchange degree (%)                                                           40    56     20    20     26                                 Rare earth metal oxide amount (wt %)                                                           1.15  1.36   1.18  0.79   0.81                               Results of cracking                                                           Conversion (wt %)                                                                              65.0  65.0   66.1  66.4   66.2                               Hydrogen (wt %)  0.14  0.13   0.17  0.21   0.21                               C.sub.1 -C.sub.2 (wt %)                                                                        1.5   1.8    1.6   1.7    1.8                                LPG (wt %)       11.3  10.8   11.7  13.7   13.2                               Gasoline (wt %)  49.8  50.1   49.8  46.6   46.4                               LCO*.sup.1 (wt %)                                                                              23.7  23.0   22.1  24.4   24.2                               HCO+*.sup.2 (wt %)                                                                             11.3  11.2   11.8  9.3    9.7                                Coke (wt %)      2.3   2.2    2.7   4.1    4.5                                Olefins (vol %)  44.0  43.7   47.4  45.9   45.0                               Catalytic Activity*.sup.3                                                                      66    62     62    66     64                                 Group for evaluation                                                                            II!   II!    II!   III!   III!                              __________________________________________________________________________     *.sup.1 : Light cycle oil fraction having a boiling range of about 190 to     350° C.                                                                *.sup.2 : Heavy cycle oil fraction having a boiling range of from about       350° C.                                                                *.sup.3 : Conversion at a catalyst/oil ratio of 7.                       

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereto.

What is claimed is:
 1. A process for producing a crystallinealuminosilicate having the following characteristics:(A) an SiO₂ /Al₂ O₃molar ratio as determined by chemical analysis of from 5 to 11; (B) aunit cell dimension of from 24.45 to 24.55 Å; (C) a molar ratio of theAl contained in the zeolite framework to the total Al contained in thealuminosilicate of from 0.3 to 0.9, said molar ratio being calculatedusing the following equations (1) to (3):

    N.sub.Al =(a.sub.0 -2.425)/0.000868                        (1)

where a₀ is the unit cell dimension (nm) and N_(Al) is the number of Alatoms per unit cell,

    (Si/Al)=(192-N.sub.Al)/N.sub.Al                            ( 2)

where 192 is the number of Si and Al atoms per unit cell of zeolite Y,and (Al in the zeolite framework)/total (Al)={(Si/Al) determined bychemical analysis}/{(Si/Al) determined by using equation (2)} (3) (D) analkali metal content, in terms of oxide, of from 0.02 to 1.5% by weight;(E) an X-ray diffraction pattern having peaks characteristic of zeoliteY; and (F) an ignition loss of from 0.5 to 20% by weight; which processcomprises calcining stabilized zeolite Y in the temperature range offrom 400° to 590° C. for 5 to 300 minutes such that the decrease in thecrystallinity of said stabilized zeolite Y is 20% or less, saidstabilized zeolite Y initially having an SiO₂ /Al₂ O₃ molar ratio offrom 5 to 11, a unit cell dimension of from 24.50 to 24.72 Å, and analkali metal content in terms of oxide of from 0.02 to 1.5% by weight.2. The process as claimed in claim 1, wherein the calcination isconducted in a temperature range of from 450° to 570° C. for 5 to 100minutes.
 3. The process as claimed in claim 1, wherein the calcinationis conducted in either an air, a nitrogen, or a steam atmosphere.
 4. Theprocess as claimed in claim 1, wherein the calcination is conducted suchthat the decrease in the crystallinity of the stabilized zeolite Y is15% or less.